Wall construction



Feb. 24, 1970 H. o. LUTGENDORF 3,496,726

WALL CONSTRUCTION Filed Nov. '7, 1967 States Pate Unite Int. Cl. 1221a 5/00,- iEZlb 17/00, 41/00 US. Cl. 6141 18 Claims ABSTRACT OF THE DTSCLOSURE A structure, particularly a lining construction for deep shafts in water-bearing rock formations, comprising in combination, an outer tubular member having an inner face, and an outer face subjected to radially inwardly acting exterior compressive stresses within a range whose upper limit is sufiicient to collapse the outer tubular member, an inner tubular member concentrically arranged within the outer tubular member and having an external surface defining with the inner face an annular clearance, and a body of fiowable medium confined within the annular clearance, the fiowable medium exerting on the inner face a counterpressure of a magnitude sufficient to counteract a fraction of the compressive stresses, and exerting on the external surface a radial pressure corresponding to the difference between the counterpressure and the compressive stresses, whereby the outer tubular member is relieved and protected against collapse by the compressive stresses.

Background of the invention The present invention relates to a wall construction, and more particularly to a wall construction which lines shafts sunk into the ground.

When a shaft, usually a rather deep shaft, is sunk into the ground, and more particularly into water-bearing rock or into water-bearing roof rock, the shaft lining is subjected to a variety of stresses. Evidently, there are axial stresses resulting from the weight of the lining itself. There are pressures exerted upon the lining by the rock itself as a result of shifts in the rock formations and such pressures usually act asymmetrically, but primarily there is the hydrostatic pressure of the water in the rock formation. This water pressure acts centrically symmetrically upon the exterior of the shaft lining and it is of course clear that the deeper the shaft is, the greater will be the Water pressure. Where the roof rock stratum is not solid and supports the covering soil, the soil pressure is superimposed upon the hydrostatic pressure.

To counteract all this it is necessary to significantly increase the wall thickness of the shaft lining as the depth of the shaft increases. In deep shafts sunk in waterbearing rock formations, or in shafts which are sunk in relatively deep water-bearing roof rock, this necessary increase in the wall thickness of the shaft lining means that the strength of the material from which the lining is constructed cannot be utilizer, or not be sufficiently utilized, because the tangential horizontal compressive stresses within the wall of the usually cylindrical shaft lining are unevenly distributed over the wall thickness in such a manner that the thicker the wall is, the greater will be the magnitude of stresses acting at the inner side of the wall over those acting at the outer side of the wall. It i evident that this condition adversely affects the economics of constructing such shaft linings, particularly in the aforementioned types of water-bearing rock formations. Moreover, while shaft linings of steel concrete and bonded masonry are particularly affected by this problem, it has been found that other materials suitable for construction of the Walls of the shaft lining are also affected so that the problem cannot be overcome by switching to a different material.

What has been said so far concerns single-wall shaft linings. However, the same problems affect dual or multiple-wall shaft linings if there is a unitary connection between the individual walls because the thus connected multiple walls will then act in effect in the same manner as a single wall, with the tangential compressive stresses being unequally distributed over the total wall thickness of both or all of the walls and of the layer or layers connecting the same. The problem can be somewhat reduced in bonded or compound structures of this type if for instance the inner wall is made from a more resistant material which is better able to withstand the higher tangential compressive stresses which act upon the inner wall as compared to the outer wall, but in view of the fact that the radial deformation of all walls is necessarily identical, the possibility of such compensation is strictly limited.

Many attempts have of course been made to overcome this problem, but none of them have been very satisfactory because even in constructions Where the lining consists of two or more walls, it has never been possible until now to arrive at a solution in which the innermost wall is not required to absorb the major compressive stresses, or in which the compound lining consisting of two or more joined-together walls is not subject to similarly joint deformation, with the result that the undesirably increased thickness of the individual or compound wall is always present in these prior-art constructions.

Summary of the invention The present invention overcomes these disadvantages.

More particularly, the present invention provides a wall construction, particularly a lining for shafts, wherein compressive stresses acting against the exterior of the lining are so distributed that the wall thickness can be reduced to such an extent as to make possible optimum utilization of the properties inherent in the material used in the construction of the Wall.

In accordance with a feature of my invention I obtain the realization of my goal by providing a wall construction for shaft linings which consists over at least a portion of its height of two or more discrete cylindrical wall members which are arranged concentrically with clearance from one another. The clearance between adjacent ones of the wall members houses a filler material which is either liquid or which has hydrostatic properties substantially analogous to those of a liquid, and which is non-hardening. The use of such a filler material permits relative movement of the cylindrical wall members with reference to one another if the width of the respective annular clearances between adjacent ones of the cylindrical wall members is selected sufliciently large, usually in a range which may vary between approximately one and several decimeters, and makes it possible to so select the side thrust of the filler material against the adjacent cylindrical wall members, which are of course made impenetrable to the filler material, that this side thrust, insofar as it acts against the inner side of one of the discrete cylindrical Wall members, is significantly lower than the corresponding side thrust which acts centrically against the exterior of this same wall member. With this arrangement I make it possible in a most simple and reliable manner to transmit the pressure exerted against the outermost wall member in exactly the predetermined proportions to one or more inner discrete cylindrical wall members, and to thereby relieve the outermost wall member accordingly. This apportionment can be achieved in various different ways, for instance by selecting filler materials of different specific weight for the different annular g The load distribution to the individual discrete wall members can be freely selected within relatively wide boundaries and independently of the relative deformation of the individual cylindrical wall members, and in all circumstances my invention assures that the total wall thickness for shaft linings in shafts which are sunk to relatively great depths is significantly less than is the case even with single-wall shaft linings, with the resultant savings in material. Clearly, therefore, the shaft lining according to my present invention is thus considerably more economical than prior-art constructions, while offering no reduction in safety, and this is particularly true because the invention offers great flexibility in the selection of materials. Thus, the discrete cylindrical wall members may be constructed of steel, steel concrete, compound materials or the like, and the selection can be freely made depending upon which type of construction and which material will be most economical under the existing circumstances.

It has already been pointed out that various different approaches may be utilized to obtain the desired stress distribution from the outermost to one or more inner cylindrical wall members. The simplest way to achieve this is to vary the specific weight of the filler material in the different annular gaps. If for instance the filler material is a stable dispersion of solid materials in water, then the specific weight can be readily varied by varying the proportion of solids. However, it is clear that in place of dispersions of solids in liquids it is also possible to use pure liquids having different natural specific weights, or even to use plastic or viscous masses, for instance on a bituminous base, whose hydrostatic properties assure that they will act analogously to liquids. The specific weight of such masses can be varied, for instance by admixture with other materials, to such an extent that they are capable-assuming an identical level in the annular gapsof opposing the thrust exerted against the outside of one of the discrete cylindrical wall members with a counterpressure acting against the inside of the same wall member but so reduced that the wall member is required to withstand only the differential remaining between the two oppositely acting pressures.

Of course, compensation by utilizing different specific weights can be avoided, or supplemented if desired, by reducing the counterpressure in any one annular gap and acting against the respective outer cylindrical wall member bounding such gap by reducing the level of filler material in the gap. Thus, the counterpressure acts only against the lower portion of the respective outer cylindrical wall member and compensation is achieved in this way. If this solution is used, then it is clear that the inner cylindrical wall member bounding such an annular gap need have only a height corresponding to the filling level. However, regardless of the type of solution utilized in accordance with the above-enumerated possibilities, it is advantageous that the pressure relationships between the discrete cylindrical wall members he so differentiated that the pressure in the annular gap between two adjacent ones of the wall members is lower than the pressure exerted against the outside of the outermost one of the two wall members by a factor ranging between approximately 25% and a maximum of approximately 75%. As a general rule I prefer that there be an approximately even distribution of the pressure acting against the outermost of the wall members to all of the wall members involved, so that if there is only one outer and one inner wall member, each of them will carry approximately half This, however, is an arrangement which is to be underof the load, and if there are two inner and one outer wall member each of them will carry approximately one-third of the load exerted against the outermost wall member.

stood as being generally desirable without constituting a limitation, it being evident that it is easily possible and in some cases even advantageous to have the various wall members carry different portions of the load. Thus, the outermost wall member may, for instance, be required to carry the major portion of the load and the inner wall members may carry the minor portion of the load which may again be evenly or unevenly distributed to them.

It is of course obvious that my invention can be so utilized that, in a manner already known in the art, the outermost wall member will be separated by an annular gap filled with liquid, or another filler material whose hydrostatic properties equate those of a liquid from the surrounding rock so that sliding movement of the individual discrete wall members is possible not only relative to one another, but also relative to the surrounding rock formation. It is, however, equally possible to connect the outermost wall member with the surrounding rock, also in known manner, so that it is fixed with reference to the surrounding rock formation, in which case only the inner cylindrical wall member or wall members serving to relieve the outermost wall member are capable of performing relative sliding movements. Regardless of which type of arrangement is utilized, and regardless of which means of transmitting pressure from one to the other of the cylindrical wall members is employed, it is always possible to so dimension the wall thickness of the individual wall members that the material of which the respective Wall members consist will be utilized to the maximum permissible limit at the inside of the respective wall member so that each of these wall members can be designed for maximum economy of construction, independently of any of the other wall members involved.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

Brief description of the drawing FIG. 1 is a schematic longitudinal section of an arrangement incorporating one embodiment of my invention; and

FIG. 2 is a view substantially similar to FIG. 1, but illustrating another embodiment of my invention.

Description of the preferred embodiments Discussing now the drawing in detail, and firstly FIG. 1 thereof, it will be seen that reference numeral 1 identifies the upper portion of a shaft which is sunk into a rock formation, and whose upper open end is designated with reference numeral 4. The lower portion of the shaft is identified with reference numeral 5. The rock formation, namely a water-bearing rock formation, is identified with reference numeral 2 and the portions of the rock formatiton which will exert inwardly directed thrust are identified with reference numeral 3. The lower portion of the shaft, namely the portion 5, is lined by a single cylindrical wall member 6 in conventional manner, and arranged atop this wall member 6 is a bearing or support ring 7 which rests on a shoulder created in the rock formation as a result of the fact that the upper portion 1 of the shaft has a greater diameter than the portion 5 thereof. The wall member 6 and the support ring 7 both consist of concrete in the illustrated embodiment.

The shaft lining according to the embodiment illustrated in FIG. 1 of the invention rests on and is supported by the ring 7. In this embodiment the shaft lining consists of three concentrically arranged cylindrical wall members 8, 9 and 10 each of which extends to the upper open end 4 of the shaft. The Wall members are arranged with radial spacing from one another so that clearances or annular gaps 11, 12 and 13 exist therebetween which in the illustrated embodiment are assumed to have a width of approximately 8 cm. and which, as already pointed out earlier, may have a width ranging between substantially 1 decimeter and several decimeters, a decimeter being one-tenth of a meter.

In accordance with the present invention the annular gaps 11, 12 and 13 are each filled in the illustrated embodiment of FIG. 1 with a fluid, with the fluids in the different annular gaps having different specific weights. More precisely, the embodiment of FIG. 1 assumes that the fluid in the annular gap 12 has a specific weight which is approximately one-third less than the specific weight of the fluid in the outermost annular gap 13, whereas the fluid in the annular gap 11 has a specific weight which is substantially two-thirds lower than the specific weight of the fluid in the gap 13. Thus, each of the cylindrical wall members 8, 9 and is required to withstand only the resulting stress differential so that the stresses which act upon the outermost wall member 10 are substantially evenly distributed to all of the wall members 10, 9 and 8. This being the case it is clear that the wall members can all be of substantially identical wall thickness, and in view of the fact that stresses distribution in thin-walled cylindrical members is considerably more advantageous than in thick-walled members of this type, the combined wall thickness of all three members together can be significantly less than would be the case in a shaft of corresponding depth utilizing a single-wall lining. It follows from this that the quantities of material required are accordingly also smaller. This, of course, is true not only of a comparison with single-wall shaft liners, but also of the type of prior-art construction wherein the shaft liner consists of two or more concentric walls which are, however, connected or joined into a monolithic unit in the manner which has been discussed earlier.

Coming now to the embodiment illustrated in FIG. 2 it will bee seen that this differs from that illustrated in FIG. 1 in that the hydrostatic pressure in the various annular gaps is varied not by using fluids of different specific weight, but by reducing the level of fluid in the various gaps. Reference numerals 1-7 again identify the same elements as in FIG. 1. The three cylindrical wall members, however, are in FIG. 2 identified with reference numerals 14, 15 and 16, with reference numeral 14 identifying the innermost and reference numeral 16 identifying the outermost one of these wall members. The annular gaps between the wall members 1416 are identified with reference numerals 17, 18 and 19, respectively.

Unlike the embodiment of FIG. 1, the embodiment illustrated in FIG. 2 utilizes annular wall members of differential height. Thus, the outermost annular wall member 16 extends from the support ring 7 to the open end 4 of the shaft. The wall member 15, which is inwardly adjacent to the wall member 16, extends from the support ring 7 only part of the way to the open end 4 of the shaft, namely substantially two-thirds of this distance. Finally, the innermost wall member 14 extends from the support ring 7 only one-third of the distance towards the open end 4 of the shaft. With this arrangement the fluid filling the annular gaps 17, 18' and 19 may have identical specific weight in each case and the load or stress distribution from the outermost annular member 16 to the innermost annular member 14 is effected by exerting inner counter pressure upon the respective outer annular member, namely either the outer annular member 16 or the outer annular member 15, only over that portion of the height thereof which would be subjected to excessive stresses in the absence of such inner counterpressure, or which would otherwise be required to have in this portion of its height an excessively great wall thickness because of the disadvantageous stress distribution. Of course, the embodiment illustrated in FIG. 2 is particularly saving in the use of materials because of the height differential between the annular members, and because of the lesser quantities of filler fluid required for filling the annular gaps therebetween.

It is clear that under certain circumstances it may be desirable and/or advantageous to use for the various annular gaps filler fluids of different specific weights, just as in the embodiment of FIG. 1, and there is no reason why resort should not be had to this. It is also clear that the height of the annular members with reference to one another need not be selected as illustrated in FIG. 2, but can be different, depending upon the requirements of a given situation, so that for instance the height of the member 15 may be one half of the member 16, and the height of the member 14 may be one-quarter that of the member 16.

In both of the illustrated embodiments the outermost annular member has been shown as separated from the thrust-exerting rock formation 3 by a gap filled with fluid so that the outermost annular members 10 in the case of FIG. 1 and 16 in the case of FIG. 2, have freedom of movement with reference to this rock formation 3. However, and as has already been pointed out earlier, the respective outermost annular members can be directly connected to the rock formation 3 so as to be precluded from performing movements relative thereto and this does not influence the concept of the present invention, nor the validity of the observations made above with reference to the operation and effectiveness of the structure according to the invention. Furthermore, it will be evident that the invention is by no means limited to use in only the upper portion 1 of a shaft. It is clearly within the scope of the invention to use the inventive structure only in the lower portion 5 of the shaft, in an intermediate portion of the shaft, in two or more axially spaced portions of the shaft, or over the entire height of the shaft. In all such circumstances that portion of the shaft in which the inventive construction is not used can be lined in conventional manner. The decision on which portions of the lining to construct in accordance with the present invention, will depend on the requirements and circumstances of a given situation, and it is evident that the construction according to the present invention should be employed whereever a significant hydrostatic side thrust, with or without superimposed thrust of the covering soil, is exerted upon the outer wall of the shaft lining, a situation which normally obtains in water-bearing rock formations and particularly in water-bearing non-solidified roof rock formations.

The advantages of the present invention are obvious and are constituted not only by the increased economy of such constructions, but also by their relative simplicity and by the fact that safety is not sacrificed to economy and simplicity.

It will be understood that each of the elements de scribed above, or two or more together, may also find a useful application in other types of wall constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a wall construction which is particularly suitable for a shaft lining, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as now and desired to be protected by Letters Patent is set forth in the appended claims:

1. A lining construction for shafts comprising, in combination, a vertical outer tubular lining member arranged within said shafts; means creating against the outer surface of said vertical outer tubular lining member a static fluid pressure increasing in downward direction of said vertical outer tubular lining member; a vertical inner tubular lining member arranged concentrically within said vertical outer tubular lining member spaced therefrom so as to form an annular space between said lining members; and a flowable medium located within and at least partly filling said annular space and being of such nature and so arranged that at each horizontal level the static fluid pressure exerted against the outer surface of said vertical outer annular lining member is greater than the static fluid pressure at the same horizontal level within the flowable medium in said annular space and acting upon said vertical inner tubular lining member.

2. A structure as defined in claim 1, wherein said flOW- able medium is liquid.

3. A structure as defined in claim 1, wherein said flowable medium is a medium having hydrostatic properties at least substantially corresponding to those of a liquid.

4. A structure as defined in claim 1, wherein said flowable medium is a viscous medium having hydrostatic properties at least substantially corresponding to those of a liquid.

5. A structure as defined in claim 1, wherein said tubular members are substantially vertical.

6. A structure as defined in claim 5, wherein said lining members and said annular spaces are substantially coextensive with said outer tubular member.

7. A structure as defined in claim 1, wherein the radial width of said annular spaces range between substantially one-tenth and several tenths of a meter.

8. A structure as defined in claim 1, further comprising an additional tubular lining member concentrically arranged within said inner tubular lining member and defining with the same an additional annular clearance; and additional flowable medium confined within said additional annular clearance, the flowable medium in said additional annular space having a specific weight other than that of the flowable medium in said intermediate annular space so that some of the radial pressure acting upon said inner tubular member is transmitted to said additional tubular member and said inner tubular member is thereby relieved.

9. A structure as defined in claim 1, wherein the pressure within said outer annular space is lower than the compressive stresses acting upon said outer tubular mem ber by between substantially and a maximum of substantially 75%.

10. A structure as defined in claim 5, further comprising an additional tubular lining member defining with said inner tubular lining member an additional annular clearance; and additional flowable medium confined within said additional annular clearance, said members and flowable media being so arranged that compressive stresses exerted upon said outer tubular member are borne in substantially equal parts by all of said members.

11. A structure as defined in claim 9, wherein the radial pressure exerted on said inner tubular lining member corresponds to substantially half the magnitude of said compressive stresses.

12. A structure as defined in claim 10, wherein said inner tubular lining member is longitudinally coextensive with only a lower portion of said outer tubular lining member, and said additional tubular member is longitudinally coextensive with only a lower portion of said inner tubular lining member.

13. A structure as defined in claim 5, wherein said members are received in a shaft provided in a rock formation, said outer tubular member being slidably movable With reference to the rock bounding said shaft.

14. A structure as defined in claim 13, wherein said outer tubular member defines an annular gap with the rock bounding said shaft; and further flowable medium confined in said annular gap.

15. A structure as defined in claim 14, wherein said further flowable medium has a specific weight greater than that of said flowable medium in said outer annular space.

16. A structure as defined in claim 14, wherein said further flowable medium fills said annular gap to a level higher than the level of said flowable medium in said outer annular space.

17. A lining construction for shafts having an inner circumferential surface, said construction comprising, in combination, a vertical outer tubular lining member arranged within said shaft in pressure-transmitting relationship with said inner surface and having an outer surface exposed to a static fluid pressure which increases in downward direction of said vertical outer tubular lining member; a vertical inner tubular lining member arranged concentrically within said vertical outer tubular lining member spaced therefrom so as to form an annular space between said lining members; and a flowable medium located within and at least partly filling said annular space and being of such nature and so arranged that at each horizontal level the static fluid pressure exerted against the outer surface of said vertical outer annular lining is greater than the static fluid pressure within the flowable medium in said annular space at the same horizontal level and acting upon said vertical inner tubular lining member.

18. A lining construction for shafts comprising, in combination, a vertical outer tubular lining member arranged within said shaft; means creating against the outer surface of said vertical outer tubular lining member a static fluid pressure increasing in downward direction of said vertical outer tubular lining member; a first inner vertical tubular lining member arranged concentrically within said vertical outer tubular lining member and having an external surface spaced therefrom so as to form a first annular space between said lining members; a second inner vertical tubular lining member arranged concentrically within said first inner vertical tubular lining member to form therewith a second annular space; and flowable medium located within and at least partly filling said first and second annular spaces and being of such nature and so arranged that at each horizontal level the static fluid pressure exerted at the same horizontal level against the outer surface of said vertical outer annular lining is greater than the static fluid pressure within the flowable medium in said first annular space and the static fluid pressure exerted against the external surface of said first vertical inner tubular lining member is greater than the static fluid pressure within the flowable medium in said second annular space.

References Cited FOREIGN PATENTS 757,827 9/1956 Great Britain.

JACOB SHAPIRO, Primary Examiner US. Cl. X.R. 

